Desire is neutral in the abstract, but not in the real world. Its good or evil is determined not simply by its object but also by the desirers motivations. Desire is mimetic. It’s harder to live in densely populated areas for this reason. This also explains why our happiness is predicated to highly on our success relative to our neighbours. In a densely populated area your neighbours are both more numerous and more varied.
You could say that these thoughts about desire explain the root of almost all rivalry and therefore violence. In fact, I find very little to disagree with here:
Girard describes this as a process of triangulation. We see somebody desiring an object. Due to imitation I begin to desire the same object. And with both of us desiring the same object a rivalry forms between us. This–mimetic rivalry–is the root cause of violence.